fix(utilization_metric): run a separate task for utilization to ensure it is regularly published

[esensar]

Summary

This adds a separate task that runs periodically to emit utilization metrics and collect messages from components that need their utilization metrics calculated. This ensures that utilization metric is published even when no events are running through a component.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Ran vector with internal metrics and observer that utilization was updated every ~5 secs, instead of only when events are running.

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run dd-rust-license-tool write to regenerate the license inventory and commit the changes (if any). More details here.

References

• Closes: Prometheus stats "stuck" on last value seen for transforms using aggregations (vector_utilization) #20216

[esensar]

I have left this as a draft, since I am not sure how to handle shutdown (which shutdown signal to use) and how to name the task (or maybe run it in a completely different way, to not mix it up with components).

Also, gauge is passed into the timer instead of using the macro inside the timer to ensure that correct labels are inherited from the tracing context.